The historic core of the town, with Holy Trinity Church at its heart, retains a sense of history and architecture. The 13th-15th century church, with its raised churchyard provides the centrepiece and landmark.
The churchyard walls topped with cast-iron railings circumvent Church Street and the historic granite slabbed pavement and later Victorian fountain provide echoes of the centuries of history in this place. The Grade l listed parish church; Holy Trinity Church is the oldest building in St Austell town.
Much of the church dates from the 13th, 14th and 15th centuries, and features a Norman font and other historic interior architectural features. One of the stained glass windows depicts Bishop Colenso of Natal, who is thought to have been born in High Cross Street.
The west end is of Pentewan stone and the remainder a mixture of both fine-grained granite and Pentewan stone. Records show a church has been here since 1169. Its 15th century tower stands high in the town, faced in Pentewan stone. The original clock face has a 24hour dial instead of the usual 12.
The finest architectural feature is the 3-stage tower with buttresses offset from the corners, strings dividing the stages, the parapet string pierced by carved gargoyles; corbels carry the octagonal corners of the upper stage rising to crocketted pinnacles. There are niches with carved figures to each side of the 2nd stage, 4 apostles to each side except the west side which has a pyramid arrangement of 6 with the top 3 representing the Trinity and the Annunciation, and the risen Christ between 2 saints below thought to be St Mewan and St Austell – the legendary founder of the town. In the church yard is a granite cross, found in 1879 on the Manor of Treverbyn and erected in churchyard in 1891.